Prior to the present invention, self-supporting carbon fiber structures suitable for molten silicon infiltration to produce silicon-silicon carbide composites were generally made by machining a preform which could be made from carbon fiber or filaments and a suitable binder, such as molten wax or colloidal graphite, etc., as shown in Laskow et al, U.S. Pat. No. 4,141,948, assigned to the same assignee as the present invention. However, in view of the increased interest toward the use of silicon-silicon carbide refractories having intricate shapes without the need for machining with abrasives as provided by the aforementioned Laskow et al method, renewed interest has been applied to the development of procedures for making the molten silicon infiltratable carbon fiber preforms by techniques other than by machining.
The present invention is based on the discovery that shaped self-supporting carbon fiber structures can be made by a slurry casting procedure similar to slip casting based on the pouring of a curable mixture of carbon fiber and binder into a mold, followed by the removal of excess binder by the application of reduced pressure. The resulting carbon fiber having residual binder can be readily converted to a self-supporting shaped structure by allowing the binder to cure or by effecting its cure, such as by subjecting it to heat or radiation and thereafter providing for the removal of the shaped carbon fiber structure from the mold.